Messages in this thread Patch in this message | | | Date | Fri, 11 Aug 2017 18:47:04 +0200 | From | Daniel Borkmann <> | Subject | Re: [RFC PATCH 2/2] bpf: Initialise mod[] in bpf_trace_printk |
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Hi James,
On 08/09/2017 10:34 PM, Daniel Borkmann wrote: > On 08/09/2017 09:39 AM, James Hogan wrote: > [...] >> time (but please consider looking at the other patch which is certainly >> a more real issue). > > Sorry for the delay, started looking into that and whether we > have some other options, I'll get back to you on this.
Could we solve this more generically (as in: originally intended) in the sense that we don't need to trust the gcc va_list handling; I feel this is relying on an implementation detail? Perhaps something like below poc patch?
Thanks again, Daniel
From 71f16544d455abb6bb82f7253c17c14d2a395e91 Mon Sep 17 00:00:00 2001 Message-Id: <71f16544d455abb6bb82f7253c17c14d2a395e91.1502469361.git.daniel@iogearbox.net> From: Daniel Borkmann <daniel@iogearbox.net> Date: Fri, 11 Aug 2017 15:56:32 +0200 Subject: [PATCH] bpf: fix bpf_trace_printk on 32 bit
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> --- kernel/trace/bpf_trace.c | 31 +++++++++++++++++++++++++++---- 1 file changed, 27 insertions(+), 4 deletions(-)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 3738519..d4cb36f 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -204,10 +204,33 @@ static const struct bpf_func_proto *bpf_get_probe_write_proto(void) fmt_cnt++; }
- return __trace_printk(1/* fake ip will not be printed */, fmt, - mod[0] == 2 ? arg1 : mod[0] == 1 ? (long) arg1 : (u32) arg1, - mod[1] == 2 ? arg2 : mod[1] == 1 ? (long) arg2 : (u32) arg2, - mod[2] == 2 ? arg3 : mod[2] == 1 ? (long) arg3 : (u32) arg3); +#define __BPF_TP_EMIT() __BPF_ARG3_TP() +#define __BPF_TP(...) \ + __trace_printk(1 /* fake ip will not be printed */, \ + fmt, ##__VA_ARGS__) + +#define __BPF_ARG1_TP(...) \ + ((mod[0] == 2 || (mod[0] == 1 && __BITS_PER_LONG == 64)) \ + ? __BPF_TP(arg1, ##__VA_ARGS__) \ + : ((mod[0] == 1 || (mod[0] == 0 && __BITS_PER_LONG == 32)) \ + ? __BPF_TP((long)arg1, ##__VA_ARGS__) \ + : __BPF_TP((u32)arg1, ##__VA_ARGS__))) + +#define __BPF_ARG2_TP(...) \ + ((mod[1] == 2 || (mod[1] == 1 && __BITS_PER_LONG == 64)) \ + ? __BPF_ARG1_TP(arg2, ##__VA_ARGS__) \ + : ((mod[1] == 1 || (mod[1] == 0 && __BITS_PER_LONG == 32)) \ + ? __BPF_ARG1_TP((long)arg2, ##__VA_ARGS__) \ + : __BPF_ARG1_TP((u32)arg2, ##__VA_ARGS__))) + +#define __BPF_ARG3_TP(...) \ + ((mod[2] == 2 || (mod[2] == 1 && __BITS_PER_LONG == 64)) \ + ? __BPF_ARG2_TP(arg3, ##__VA_ARGS__) \ + : ((mod[2] == 1 || (mod[2] == 0 && __BITS_PER_LONG == 32)) \ + ? __BPF_ARG2_TP((long)arg3, ##__VA_ARGS__) \ + : __BPF_ARG2_TP((u32)arg3, ##__VA_ARGS__))) + + return __BPF_TP_EMIT(); }
static const struct bpf_func_proto bpf_trace_printk_proto = { -- 1.9.3
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